The IEEE 802.21 Media Independent Handover (MIH) standard defines mechanisms and procedures that aid in the execution and management of inter-access technology mobility management. IEEE 802.21 defines three main services available to Mobility Management applications. Referring to FIG. 1, these services are the Event Service 100, the Information Service 105 and the Command Service 110. These services aid in the management of handover operations, system discovery and system selection by providing information and triggers from lower layers 115 to upper layers 120, and lower layer commands from upper layers 120 to lower layers 115 via a media independent handover function (MIHF) 125. While FIG. 1 shows MIHF 125 as a middle layer in a protocol stack, MIHF 125 may also be implemented as an MIH plane that is capable of exchanging information and triggers directly with each and every layer of a technology-specific protocol stack.
Events may indicate changes in state and transmission behavior of the physical, data link and logical link layers, or predict state changes of these layers. The Event Service 100 may also be used to indicate management actions or command status on the part of the network or a management entity. The command service 110 enables higher layers to control the physical, data link, and logical link layers (referred to collectively as lower layers). The higher layers may control the reconfiguration or selection of an appropriate link through a set of handover commands. If an MIHF supports the command service, all MIH commands are mandatory in nature. When an MIHF receives a command, it is always expected to execute the command. The Information Service 105 provides a framework and corresponding mechanisms by which an MIHF entity may discover and obtain network information existing within a geographical area to facilitate handover.
The MIH standard may be applied to support handover between various radio access technologies (RATs), including wireless code division multiple access (WCDMA), IEEE 802.11x (WiFi), IEEE 802.3, IEEE 802.14, IEEE 802.16 (WiMAX), IEEE 802.16e (WiBro), Third Generation Partnership Project (3GPP) and Third Generation Partnership Project Two (3GPP2) technologies. A wireless transmit/receive unit (WTRU) may be handed over from a network of one type to another. Where a WTRU can communicate via WCDMA and WiBro technologies, it would be beneficial for the WTRU to support MIH handover from WCDMA to WiBro and from WiBro to WCDMA. Where a WTRU can communicate via WCDMA and WiFi technologies, it would be beneficial for the WTRU to support MIH handover from WCDMA to WiFi and from WiFi to WCDMA. An approach is required for a WTRU to support MIH bi-directional handover in these and other contexts. Therefore, it would be beneficial for MIH handover to be supported in a WTRU via an MIH middleware.